Movement FinishingThere are 3 main elements to the movement finishing that I do. First, Côtes de Genève. Second, perlage. Third, bluing the screws. This entry will describe the perlage process.

PerlageOf the three movement decorations, perlage is probably the easiest to do. I use a benchtop drill press and a 1/4" Cratex tip on a mandrel. But there are multiple ways to do it.

Before doing anything with the 6498, I practiced with some brass discs to get a feel for how the perlage shows up. I also experimented with the Cratex. I sanded some of the tips down to a 3mm - 4mm diameter to produce smaller perlage.

On to the movement itself...I started on the outside edge and worked my way to the center. I overlapped each circle about 1/2 way into the previous circle. I like that the result isn't perfect. To me, I believe, it adds to the handmade quality of the watch. Perlage done by CNC machines are spaced perfectly, which is fine, but I much prefer the unique pattern of the perlage when applied by hand. This will make each movement I decorate even more unique.

Movement FinishingThere are 3 main elements to the movement finishing that I do. First, Côtes de Genève. Second, perlage. Third, bluing the screws. This entry will describe the process to blue the screws.

Bluing ScrewsI took a digital soldering iron and made a custom tip out of copper with a couple of small holes drilled in it. I first made one out of brass but the soldering iron I have had a hard time heating up the brass enough to blue the screws…so that’s when I made the copper tip and it’s worked great. With the copper tip I usually set the temperature to 350 C, drop the screw in the hole and watch it turn blue, when it’s the shade I want, I pull it out w/ an old pair of tweezers and drop it into a small cup of water.

I bought a bag of screws off of eBay to practice with…and that made a big difference. Just being able to see how different the shades of blue can be. With all the practice screws I turned blue, it gave me a good feel for what color I wanted and how long it took. Most of the time the screws were on the iron for between 5-8 seconds.

Now concerning prepping the screws. All the screws are nickel plated…which won’t turn blue unless the nickel is removed. So far I have simply polished the nickel off the top of the screw…so only the polished face of the screw head turns blue. I like how they turn out w/ the slot for the screwdriver staying silver…Anyhow, to remove the nickel, I simply sand each screw on 2000 grit sandpaper then on a 3 micron lapping paper and finish polishing with Mother's Mag and Aluminum polish on a micro-fiber cloth. After they have been polished, I clean them in an ultrasonic cleaner with watch cleaning solution…then they are ready to hit the soldering iron.

Many of the screws I practiced with weren’t plated…so when they hit the iron, the entire screw turned blue…which is cool too, but the only way to get that w/ the 6498 screws would be to take them to a plating company and have the nickel removed (which I may try one day…but for this project, I just went w/ removing the nickel from the screw face).

Movement FinishingThere are 3 main elements to the movement finishing that I do. First, Côtes de Genève. Second, perlage. Third, bluing the screws. I'll first describe the process I used to apply the Côtes de Genève.

Côtes de GenèveHere's the process in a nutshell:The mill I used is a bit bigger than needed...eventually I want to get a bench top mill like a Sherline.But for now this one from Taiwan did the trick.

I used a lathe chuck to hold the Bergeon movement holder and had the bridges screwed into the base plate and the movement set in the Bergeon movement holder.This whole set up was mounted to the mill table w/ a small .02” shim under the right side.

I tried to level the movement as best I could from front to back…and we ended up with about a .0005” change from front to back.Side to side we had a .01” drop from right to left (mostly due to the .02” shim).But now that I think about it, we could have created that angle in the lathe chuck too.Anyhow, in the mill head we used a 1” dia. aluminum mandrel with a piece of 400 grit Trizact (a 3M product) super-glued to it.All the cutting is done dry – we tried lubricant, but it didn’t work…maybe it would if the lubricant was flowing over the material during the entire cutting process…but we just experimented w/ spraying a bit on our practice brass discs just to see how it worked.

Mill RPM was set at 500…we experimented and found that slower was better…we started on the right hand side and did 14 stripes at approx 2.5mm per stripe.We dropped the mill head approx .0007” per stripe to compensate for the .01” drop from right to left.

Cutting direction of the mandrel was clockwise and we pushed the movement forward into the mandrel…then recorded the mill head height, raised the mill head, pulled the movement back, moved it to the right 2.5mm, lowered the mill head to the old height minus .0007” and did another stripe.

With each pass, you are scratching about a ½” wide surface area of the movement…then, when you move over the 2.5mm and make a second pass, the stripe is created.Does that make sense?This is one thing we found out when we were doing our practice runs.I initially thought since the movement was angled, a perfect 2.5mm strip would be laid down w/ each pass…but that’s not the case…the “stripe” is easily ½” wide, then you simply put an edge one it w/ each pass. And there you go...

A couple of updates to the striping process. You need to make sure that you have as close to perfect of an edge on your mandrel. I'm currently working on a few more pieces and found that as I replaced the Trizact, the edge of the mandrel was getting a bit beat up. Also, I wasn't taking the time to perfectly trim the Trizact to the mandrel. And the result was...well, the result was nothing but crap. Take a look...this is how NOT to stripe a movement.

Once we straightened the edge of the mandrel and took care to match the edge of the Trizact with the mandrel, the stripes turned out perfectly.

The other update is a template that we built out of a scrap piece of copper. We set this up so we can screw two movements to the block, place it on the mill and go. We cut an angle in to the bottom side of the block, so the pieces sit at an angle...no more messy jig set up like in the pictures above. Now it's clean and simple to stripe the movements. It's drilled and tapped for the 6497 and I plan on adding holes for the 6498. The holes are drilled .90mm and the tap is 1.1mm. The holes for the locating pins are drilled 1mm. Thanks to my brother Mark for helping me with all the mill and lathe work.

And one last note, we found that we could feed the plates into the mill at a faster rate and get really clean stripes w/ good graining. Meaning from the time the Trizact hits the edge of the movement plates, it only takes about 4-6 seconds to make the pass. In some other practice attempts, we thought slower was better...but it's not. You want to have the plates pass rather quickly under the Trizact.